THE CHEESE SKIPPER AS A PEST IX CURED MEATS 



29 



THE PUPARIUM 



The puparia of Piophila casei vary considerably in size, the largest ones 

 of normal shape measuring about 5 by 1.5 mm. The color of purparia formed 

 by well-nourished larvae is coppery red, whereas larvae from dried beef, dry 

 cheese, or old ham form puparia which are smaller and golden yellow. Puparia 

 examined ranged from 2.5 by 0.5 mm. to 6 by 1.25 mm. A gram of puparia 

 from an old ham culture contained 482 — more than twice as many as a gram 

 of puparia formed by well -nourished maggots. Bachmann {9) measured the 

 lengths of a number of puparia and arranged the results in a frequency table. 

 The most common length was 5 mm. 



The puparia are shown in c of Figure 3, at right. They are deeply 

 wrinkled at either end, with fine circumferential lines marking the surface 

 between the intersegmental constrictions. In some puparia the latter are 

 deeply incised, whereas flattened puparia and specimens with alate margins 

 are not uncommon. Puparia formed by larvae which became wedged between 

 threads of cotton were sometimes so deeply constricted by a tight strand as to 



be nearly severed — a condition which of course made 



emergence impossible. 



Puparia frequently are attached to the surface upon 

 which they rest by a minute globule, secreted at the 

 larval anus and attaining a resinous appearance by the 

 time the puparium is completely hardened. Threads 

 of cotton (Fig. 6) become glued into this globule, 

 making the disentanglement of puparia from cotton 

 somewhat tedious. In warm, moist weather the 

 brittle consistency of this spot disappears and it may 

 soften enough to stretch into a short thread capable 

 of suspending puparia beneath the point of attach- 

 ment. With the puparium secured in place by means 

 of the globule, the adult insect is probably materially 

 aided in the struggle to emerge. 



THE PUPA 



The pupa is inclosed in a thin, white membrane, 

 the skin of the prepupal larva, which lines the 

 horny puparium. The first pigment appears in the 

 eyes, which become pink. As the time for emergence 

 approaches the insect assumes a smoky-gray color. 

 A pupa with part of the puparium is shown in 

 Figure 6. 



PUPAL PERIOD 



Fig. 6. — Pupa of Piophila 

 casei with part of the 

 puparium dissected 

 away. X 10. Threads 

 of cotton are shown 

 glued into the resinous 

 globule secreted at the 

 larval anus during the 

 process of puparium 

 formation 



At temperatures of 80 to 90° F., the pupal 

 period occupies a minimum of 5 days. From 



May 10 to June 7, 1921, no pupal period less than 7 days in length 

 was recorded in the laboratory, most of the adults emerging on the 

 eighth day. On June 8 the first 6-day period was recorded and on 

 the twentieth of that month the first 5-day period. Of 1,923 puparia 

 observed from May 10 to June 19, 250, or 13 per cent, failed to 

 produce adults. Table 11 is a consolidation of data on the pupal 

 period. Temperatures relative to the dates of emergence from May 

 19 to July 16 are recorded in Table 3. 



Table 11. — Pupal period of Piophila casei at ^Yashington, D. C, in 1921 







Number of days in pupal period 







5 



6 



7 



8 



9 



10 11 



12 



13 



Number of flies which emerged from May 10 to 

 June 19, 1921 -_-."„. 



166 j 

 166 



543 



350 



455 

 2 



145 



11 



1 



1 



1 



Number of flies which emerged from June 20 to 

 July 16, 1921 



360 29 

















